Multiple pivoted jaw adjustable nut wrench



April 26, 1955 N. KVAERNE MULTIPLE PIVOTED JAW ADJUSTABLE NUT WRENCH Filed April 6, 1953 FIG].

FIG-3.

United States Patent MULTIPLE PIVOTED JAW ADJUSTABLE NUT WRENCH Nils Kvaerne, Oslo, Norway, assignor to Aktiebolaget B. A. I-Ijorth & Co., Stockholm, Sweden Application April 6, 1953, Serial No. 347,002

3 Claims. (Cl. 81-91) The present invention relates to an automatically adjustable nut wrench or spanner having jaws displaceable in parallel relation to each other and attached at a distance from each other to a handle.

Wrenches or spanners of this type as heretofore known, have not been entirely satisfactory, either because their production needed very accurate manufacture and thus became rather costly, or because the construction did not satisfy the most important conditions for a good result of operation; the first of these conditions is, that during all adjustments the jaws are in parallel operative position and the second that the jaws grip the nut the stronger the manual force is which is applied to the wrench, irrespective of the size of the nut to be tightened.

The invention provides a wrench, the jaws of which may be produced by stamping of plate material. Further, the possible adjustment range is rather large.

According to the invention a safe and parallel interpositon of the jaws for the entire adjustment range is obtained by giving the counteracting edges of the jaws wave-shape, the waves being formed of circular arcs, the radius of which is equal to half the distance between the pivot centres of the jaws. This provides contact points between the two jaws at several places for any relative position of the interengaging jaw surfaces.

Further, the invention encompasses the geometric condition of a wrench having the property that the jaws thereof will press the stronger about the nut the more force the operator applies to the wrench. For a hexagonal nut said geometric condition is obtained by making the projection of the distance between the pivot centres of the jaws onto the parallel gripping surfaces thereof in any position of the jaws equal to or less than half of the distance between the gripping surfaces of the jaws.

If the latter condition is not fulfilled, the wrench will not be self-pressing. Thus a wrench of the type described in the Swedish Patent No. 28,754 opens its jaws when one seeks to tighten the nut, unless the jaws are pressed together by means e. g. of the fingers, which is, of course, less satisfactory. For the same reason a wrench according to the German Patent No. 355,522 is self-pressing only for the largest nut dimensions, corresponding to the largest jaw openings stated.

In order that the invention may be easily understood the same is below described by reference to the figures of the drawing, which illustrate an embodiment of the invention.

Figure 1 is a side view of the wrench with the jaws adjusted for their smallest dimension;

Figure 2 shows the same with the jaws adjusted to an intermediate position;

Figure 3 shows the same with the jaws adjusted for maximum of opening.

Figure 4 is a view, taken at right angles to the other figures and Figure 5 is a section through the handle of the wrench.

On Figure l numeral 1 designates the handle of the wrench, on which the two jaws 2 and 3 are swingably supported by means of pivots 4 and 5 respectively. The contact surfaces of the jaws 2 and 3 are each provided with a wavy edge 6, the waves of which form arcs of circles each having a radius equal to half the distance between the centres of the pivots 4 and 5. One wave top in each of the jaws has its centre at the centre of the pivot 4 and of the pivot 5 respectively.

As will be seen, by studying Figures 1-3, there are for every adjustment of the position of the jaws in rela- "ice tion to the handle 1 several points of the edges 6 of the two jaws which make contact with each other. As a result, a good connection between the two jaws is obtained, irrespective of the size of the nut for which the wrench has been adjusted.

Further, according to the invention, there is provided a. bias spring device 7, one end of which is attached to the handle at 9 and the other end of which is received in a cut-out 10 provided in jaw 3. The effect of said spring device is, that when the wrench is not in actual use the members thereof are returned to their initial position, shown on Figure 1.

For easy adjustment of the wrench for nuts of different dimensions, the back 8 of jaw 3 may be knurled for easy operation by the operators thumb.

The above mentioned geometric condition for the present construction may be found as follows:

In Figure 2, PK designates the manual force used for tightening of the nut 11, whereby the latter is subjected to a force PlXl, wherein Z is the distance from the point of action of the operators hand on the handle to the centre of the nut 11. This force is counteracted by the force caused by the friction between the threads of the nut and the threads of the bolt upon which the nut is to be tightened and which occurs when one side of the nut abuts one of the jaws at 2, while the opposite side of the nut abuts the other jaw at 3', at both places with a force Py. Then, if b is the length of a side of the nut, the rotative force acting upon the nut will be Py.b and is in equilibrium with the manual force Pz.a, The force Py at 2 seeks to close the jaws, with a force Py.d, wherein d is the distance from the force vector Py to the pivot centre 4 of the jaw 2, whereas the opposing force Py at 3 seeks to open the jaws with a force Py.C, where c is the distance between said force vector Py and the pivot centre 5 of the jaw 3.

In order that the jaws shall press the stronger against the nut the more force is exerted on the wrench, the condition then must be that:

P1 .C Py.d

or that c y.

As c=e+d-b the equation also may be written as e+db d which means, expressed in words: the projection (e) of the distance between the pivot points (4 and 5) of the jaws on to the parallel gripping sides of the jaws must be less than the length of the side (12) of the nut. With a hexagonal nut the distance between two parallel side edges thereof is somewhat less than \/3 by the length of the nut side 12. As in practice the force pair Py will attack somewhat inside of the sides 2' and 3', the condition necessary to cause the wrench to close the stronger about the nut the more force the operator applies to the wrenchmust, as above mentioned, be that the projection of the distance between the pivot centres of the jaws onto the two parallel gripping sides of the jaws is equal to or less than half of the distance between the aws.

From the above it will be understood, that it is of no importance to a satisfactory operation of the wrench whether the nut is placed deeply into or near the outside of the jaw opening.

Further it is obvious, that a wrench fulfilling the above condition may be used not only for hexagonal but also for square nuts. If the wrench is to be used for octagonal nuts-seldom used in practicethe construction must be subjected to a modification, which, however, will not be described here.

I claim:

1. A wrench comprising a handle, two jaws, each having a plane gripping surface, two pivot pins secured to the handle placed apart and each pivotally supporting one of said jaws for moving both jaws relative to a work piece held between the gripping surfaces of the jaws, the said jaws further having a wave-shaped edge composed of several circularly curved sections, the radius of each of said sections being equal to half the distance between said pivot pins and each: of said wave-shaped edges including a section having its center point located in the axis of the respective pivot point, the said wave-shaped edges being in sliding engagement with each other so as to hold said gripping surfaces of the jaws in parallel relationship and adjustable in distance relative to each other, the perpendicular distance between the pivot axis of each jaw and the gripping surface thereon being at most half of the distance between the parallel gripping surfaces in each pivotal position of the jaws.

2. A wrench according to claim 1 and further comprising a loaded spring attached to said handle and one of said jaws for biasing the two jaws into a pivotal position in which the gripping surfaces thereon are at the minimum distance.

3. A wrench according to claim 1, wherein the said handle is bifurcated on one end and the said jaws are disposed between the prongs of the bifurcated handle end, the said pivot pins traversing the prongs,

References Cited in the file of this patent UNITED STATES PATENTS 1,790,411 Dixon Jan. 27, 1931 FOREIGN PATENTS 28,098 Germany July 24, 1884 598,528 France Sept. 29, 1925 

